Measurement of the sedimentation (or ability of suspended particles to settle within a liquid, under the influence of gravity), buoyancy (or ability of suspended particles to rise in the fluid) of suspensions or precipitants or diffusion rates in a fluid medium may be useful in a variety of areas, such as medical diagnostics, mechanical/industrial processing (or processing machinery testing), environmental monitoring or the like. Such measurements may be the result of sample separation due to difference of density or a reaction between fluid suspensions and a reagent. Sedimenting particle mass, shape and size all impact sedimentation rate and these properties may be estimated from measured sedimentation rates. For example, in medical diagnostics, Erythrocyte Sedimentation Rate (ESR) is one of the most frequently performed medical laboratory tests, reflecting the rate at which red blood cells separate from the plasma due to gravity in a static vertical vessel. The sedimentation rate (measured in mm/hour) is determined macro-morphologically by measuring the distance from the top cellular level to the top of plasmatic level after 60 minutes or so of uninterrupted settling time.
There are known methods to measure the sedimentation rate of suspensions in a fluid but they each have associated disadvantages, including time to answer, sample preparation, size of equipment, cost or complexity to carry out, and the like. For example, optical techniques (such as laser sources) can only be used in a transparent bulk fluid medium.